Furnace having cyclically moving flames

ABSTRACT

By cycling the pressure of fuel gases which impinge upon an air or other oxygen-containing stream directed at an angle to the fuel gases, the gas jet pattern can be caused to sweep across the combustion zone in a furnace, e.g., a Wulff regenerative furnace. This cyclic motion varies penetration and evens out heat distribution. The cyclic changes in pressure can be accomplished by rotating members presenting varying cross-sectional areas to flow or by other devices all of which may be powered externally or powered by the energy of the flowing stream.

United States Patent 1 Luetzelschwab 1March 20, 1973 [54] FURNACE HAVINGCYCLICALLY MOVING FLAMES [75] Inventor: Wayne E. Luetzelschwab,Littleton,

[73] Assignee: Marathon Oil Company, Findlay,

Ohio

[22] Filed: Sept. 13, 1971 [2.1] Appl.No.: 179,706

[52] U.S. Cl ..432/26,431/1,432/31,

432/120, 432/227, 432/266 [51] Int. Cl ..F23n 1/02 [58] Field of Search..43l/l, 8; 239/101; 263/2, 28

['56] References Cited UNITED STATES PATENTS -1 1/1964 Cremer et al..43l/1 X FOREIGN PATENTS OR APPLICATIONS 251,742 9/1969 U.S.S.R...431/1 Primary Examiner-Charles J. Myhre Assistant ExaminerWilliam C.Anderson Attorney-Joseph C. Herring et al.

57 ABSTRACT By cycling the pressure of fuel gases which impinge upon anair or other oxygen-containing stream directed at an angle to the fuelgases, the gas jet pattern can be caused to sweep across the combustionzone in a furnace, e.g., a Wulff regenerative furnace. This cyclicmotion varies penetration and evens out heat distribution. The cyclicchanges in pressure can be accomplished by rotating members presentingvarying cross-sectional areas to flow or by other devices all of whichmay be powered externally or powered by the energy of the flowingstream.

11 Claims, 23 Drawing Figures F/GS. 5A 5B PATEI-HEUmmomn 3,721,728SHIEET 3 0F 4 GENERAL APPARATUS FRONT VIEWS OF VARIOUS VANE SHAPES SOLIDVANES FRONT VIEW TOP TOP VIEWS OF VARIOUS VANE ANGLES AND NUMBERS F/GSE6A 6B 6C 60 6E 6F Pmw m 3,721,728

' SHEEILLDFQA F/G. .7 v

IIJ 11 111/11 1 11111111 1/1/1111 FIG. 8

FURNACE HAVING CYCLICALLY MOVING FLAMES BACKGROUND OF THE INVENTION 1.Field of the Invention The present invention relates to power plants,mixed fluids with pressure activated valve (U.S. Pat. class 60, subclass39.80; With fuel metering valve (U.S. Pat. class 60, subclass 39.81);and to Combustion Bursts or flare-ups in pulses or serial pattern (U.S.Pat. class 431.1).

2. Description of the Prior Art The following prior art pertains to thegeneral field of the invention: U.S. Pat. No. 2,709,890 (to R.I-I.Goddard), which uses a rotating vaned rotor (FIG. 6) or a vibrating reedFIG. 5, which are actuated by the flowing fuel and which cause apulsation of the fuel to break up the liquid fuel stream into many finedrops in the combustion chamber; and U.S. Pat. No. 1,616,778 whichcauses pulsing in a flow line to prevent accumulation of sediment orsludge in the burner nozzle. The pulsation can be caused by a fuel valve26 which reciprocates (see FIG. 1) or by a vaned rotor 32 which rotates(see FIG. 2).

Externally powered pressure fluctuation devices have been previouslyused in U.S. Pat. No. 3,044,711 which uses perforated discs 37, 42, and47, driven by external power to modulate the flow of liquid propellant;U.S. Pat. No. 3,253,784 which uses vane 9 (see Col. 2, lines 34-35)externally powered (a sort of rotating butterfly valve) to causevariations in the volume and pressure of water in a dishwasher; U.S.Pat. No. 3,327,758 which uses rotary valve 24 driven by drive motor 70in a fuel line; and U.S. Pat. No. 3,449,913 which utilizes programmedvalve 24 for introducing separately and sequentially predeterminedamounts of a fuel and air into a combustion tube.

Other devices relating to' pulsing of fuel into combustion chambers aretaught by U.S. Pat. No. 2,945,459 which accelerates combustion bycausing vibrations of controlled frequency in a gaseous combustionsupporting media, e.g., to burn granulated coal; and British Pat.813,563 which uses a rotary slide valve to inject pulses of fuel oilinto a burner.

SUMMARY OF THE INVENTION GENERAL STATEMENT OF THE INVENTION According tothe invention, in a furnace having a stream of fuel which impinges at anangle on a stream of air or other oxygen-containing gas, to cause aflame or hot gas stream which in turn impinges upon the surface to beheated, there is provided a pulsation or cyclic variation in pressure inthe fuel stream and/or the oxygen-containing gas stream. Thisfluctuation causes the flame or hot gas stream to be moved about so thatit successively impinges on a number of different points on the surfaceto be heated. This cyclic movement reduces hot spots" and under-heatedareas as well as providing burn-off of soot or other carbon deposits.

The surface to be heated may be a hot water tank, a tube bundle in asteam generator or water heater, refractories in a regenerative furnacein which the refractories are alternately heated and then used todeliver heat to a stream of gases which alternately flow past thesurface, or a simple oven wall, etc.

UTILITY OF THE INVENTION The invention is useful in a wide variety ofheating devices including ovens, regenerative furnaces, water heaters,etc. and has the advantage of reducing carbon deposits and improvingheat distribution in such heating devices.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan section view of aconventional Wulff process furnace which is described in more detail inU.S. Pat. No. 3,366,702, U.S. Pat. application, Ser. No. 888,683 (nowallowed) and Miller, S. A., Acetylene, Its Properties, Manufacture andUses, Vol. I & 11, Academic Press, N .Y. 1965-66).

FIG. 2 is a plot of pressure vs. time for a stream of fuel measured at apoint upstream from the point of entry into the combustion zone of theWulff furnace shown in FIG. 1.

FIGS. 3a through 3d are plan views of combustion zone 18 of FIG. 1, andshow the pattern of the hot gases and flame within the combustionchamber under a succession of fuel line pressures which correspond tothose marked on FIG. 2.

FIG. 4 shows one general type of device useful for causing pressurefluctuations in fuel or air lines which consists of a rotating elementanalogous to a butterfly valve.

FIGS. 50 through 5e show substantially two dimensional rotating elementsfor use in the device of FIG. 4. FIGS. 5f and 5g are a front section anda plan section view of a three dimensional rotating element. Each of thedevices of FIGS. 5a-g present successively different cross section viewsof the path of flow through the conduit of FIG. 4 as they are rotated.FIGS. 6a-6f are views of various alternate elements for use in thedevice of FIG. 4, said views having been taken in a plane transverse tothe axis of rotation of the element.

FIG. 7 shows a bucket meter-type of device for causing pressurefluctuations. This device can be powered by the energy of the gas streamor powered externally.

FIG. 8 shows a rotating vane-type of device for causing pressurefluctuations. This device can be powered by the energy of the gas streamor powered externally.

FIG. 9 shows a surge vessel with a spring-loaded valve or control valvefor causing pressure fluctuations.

It should be understood that all of the above figures are schematic andexemplary only.

DESCRIPTION OF THE PREFERRED EMBODIMENTS STARTING MATERIALS Fuels: Fuelsfor the use of the invention may be hydrocarbons either gaseous orliquid, and powdered solids, e.g., powdered coal slurries may beutilized where desired. The most preferred fuels will be gases, e.g.,refinery fuel gas.

Oxygen-containing Gas: While pure oxygen or airsupplemented withadditional quantities of pure oxygen can be employed, air will, in mostcases, be most preferred.

Conditions: Temperature, pressure, and flow rate are not narrowlycritical and they vary over a wide range, dependent upon the particularfurnace and the effect desired. These conditions may readily beoptimized by the use of routine trial runs.

EXAMPLE I Referring to FIG. 1, in the heat cycle of a Wulff furnace,refinery fuel gas enters through inlet 26 and its counterpart on theopposite side of the furnace and air enters through inlets 30, coolingrefractory stack 8, then mixes with the fuel in combustion chamber 18,burns, heating refractories of stacks l2 and 14 and off gases exitthrough outlet 31. Similar quantities of fuel and air later entercombustion chamber through corresponding inlets in the other end of thefurnace, but this discussion will be continued with respect tocombustion chamber 18, taken alone for purposes of clarity.

The fuel line, feeding fuel inlet 26 with a refinery fuel gas, is fittedwith the pressure fluctuating device shown in FIGS. 4 and 5a. As theelement shown in FIG. 5a rotates under external power, the pressure atthe inlet 26 fluctuates as shown in FIG. 2. The pressure under which theair stream enters the combustion chamber 18 remains constant. Thus, thedegree of deflection of the flame and hot gas stream 32 varies as shownin FIGS. 30 through 3d. When the pressure is high (at P-max of FIG. 2),the flame 32 extends out almost transverse to the flow of air as shownin FIG. 3a. When the pressure drops (at P-min in FIG. 2), the flame 32is greatly deflected by the air stream as shown in FIG. 3d.

This sweeping of the flame across the interior surface of therefractories of the center stack 12 of the Wulff furnace causes auniformity in the heating of the refractories preventing hot spots andaiding in burning off carbon deposits.

The residence time of the flame at any point on the interior surface ofthe center stack of refractories can be optimized by employing variousshapes of vanes as shown in FIGS. Sb-Sg and 6a-6f. Also, a series ofinlet nozzles can be utilized so that the flames vary in a coordinatedmanner sweeping gradually back and forth across various levels of theinterior surface of the refractory center stack.

MODIFICATIONS OF THE INVENTION It should be understood that theinvention is capable of a variety of modifications and variations whichwill be made apparent to those skilled in the art by a reading of thespecification and which are to be included within the spirit of theclaims appended hereto.

FIG. 7 shows a wet bucket meter-type of pressure fluctuating devicewhich can be installed in the fuel line in lieu of the device of FIG. 4for operation generally as described above. In FIG. 7, the gas entershousing 39 through the inlet 40 into the bucket 41 in position A. Thisgas displaces the liquid 42 and causes the bucket to rise to position B,at which point gas begins to exit from the bucket and eventually throughoutlet 43. By the time the bucket reaches position C the gas has beendisplaced and the bucket moves to position D completely filled withliquid. This operation results in an interrupted gas flow where both themagnitude and frequency of the cycle can be controlled by proper design.Liquid height, volume of each bucket (not necessarily the same), numberof buckets, bucket shapes, and resistance to rotation (hindered byfriction,

latches, etc.) are all design variables to obtain the desired frequencyand cycle shape.

FIG. 8 shows a rotating vane or gear-type of fluctuation device for usein place of the device of FIG. 4. The vanes (or gears) 51 are rotated bythe flow of gas through pipe 53 into housing 55. Vanes 51 may also havebucket attachments 52 to help interrupt flow to a greater degree. Toenhance the variation in flow, ad ditional resistance to rotation can beadded in the form of friction, catches, etc. The vane spacing (notnecessarily equal), number of vanes, vane shape (some could be narrow tobypass some flow), and resistance to rotation (friction, catches, etc.)are all design variables to obtain the desired frequency and cycleshape.

While not narrowly critical, rotation speeds (cycle) will preferably bein the range of 0.01 to 500, more preferably 0.1 to I00, and mostpreferably 0.3 to 50 seconds per revolution (cycle).

FIG. 9 shows a surge-tank combined with a springloaded release or othercontrol valve for providing a fluctuating pressure in the fuel line inplace of the device of FIG. 4. The gas enters inlet 61 and leaves byexit 62. Valve 63 can be any valve that will cycle either on its ownsuch as relief valves or back pressure control valves set up in a cyclicmode of operation or a programmed control valve. Surge volume 64 isrequired only when the fuel gas delivery capacity at inlet 61 is lessthan the maximum desired withdrawal rate through exit 62.

What is claimed is:

1. In a furnace having a combustion zone in which a stream ofoxygen-containing gas and a stream of fuel impinge at an angle to form aflame or hot gas stream which in turn impinges upon a surface to beheated, the improvement comprising cyclically varying the mass flow rateof at least one of said oxygen-containing stream and said fuel stream soas to vary the point of impingement of said flame or hot gases upon saidsurface to be heated.

2. A process according to claim 1 wherein said furnace is a regenerativefurnace having masses of refractories onto which said flame or stream ofhot gas is impinged.

3. The process according to claim 1 wherein at least one of saidoxygen-containing stream and said fuel stream enters said combustionzone through a constricted inlet fed by a conduit and wherein thepressure at said constricted inlet is varied by pressure varying meansin communication with said conduit.

4. A process according to claim 3 wherein said pressure varying means isa surge tank connected to a down stream valve operated in response tothe pressure in said surge tank.

5. A process according to claim 3 wherein said pressure varying meanscomprises a rotating element located within said conduit and having aconfiguration which cyclically presents varying cross-sectional areas inthe plane transverse to flow through said conduit.

6. A process according to claim 5 wherein said rotating element ispowered by external power means.

7. A process according to claim 5 wherein said rotating element issubstantially a disc.

8. A process according to claim 5 wherein said rotating element is asolid having various cross-sectional areas in the plane transverse togas flow.

6 9. A process according to claim 5 wherein said rotatbustion chamber,ing element is powered by power means driven by the d. oxygen-containinggas inlet means communicating energy of the gas Stream flowing throughSaid conduit with said combustion chamber directed at an angle 10. Aprocess according to claim 9 wherein said to id f l i l means,

rotating element comprises a series of rotatable vanes 5 whose axis ofrotation is. spaced a distance from the longitudinal center line of saidconduit, and is substantially perpendicular to said longitudinal centerline of said conduit.

11. Apparatus for the heating of surfaces by the com- 10 bustion offluids, said apparatus comprising the come. conduit means communicatingwith at least one of said fuel inlet means or oxygen-containing gasinlet means,

f. pressure fluctuation means operably located in relation to saidconduit so as to cause intermittent pressure variation in said conduit,

binatiow whereby said pressure variation causes a hot gas or a aSu'rface to be heated flame stream produced by the combustion of saidfuel a b. a combustion chamber communicating with said m commit wlthsald oxygencomammg gases to move Surface across said surface to beheated. 0. fuel inlet means communicating with said com-

1. In a furnace having a combustion zone in which a stream ofoxygen-containing gas and a stream of fuel impinge at an angle to form aflame or hot gas stream which in turn impinges upon a surface to beheated, the improvement comprising cyclically varying the mass flow rateof at least one of said oxygencontaining stream and said fuel stream soas to vary the point of impingement of said flame or hot gases upon saidsurface to be heated.
 2. A process according to claim 1 wherein saidfurnace is a regenerative furnace having masses of refractories ontowhich said flame or stream of hot gas is impinged.
 3. The processaccording to claim 1 wherein at least one of said oxygen-containingstream and said fuel stream enters said combustion zone through aconstricted inlet fed by a conduit and wherein the pressure at saidconstricted inlet is varied by pressure varying means in communicationwith said conduit.
 4. A process according to claim 3 wherein saidpressure varying means is a surge tank connected to a down stream valveoperated in response to the pressure in said surge tank.
 5. A processaccording to claim 3 wherein said pressure varying means comprises arotating element located within said conduit and having a configurationwhich cyclically presents varying cross-sectional areas in the planetransverse to flow through said conduit.
 6. A process according to claim5 wherein said rotating element is powered by external power means.
 7. Aprocess according to claim 5 wherein said rotating element issubstantially a disc.
 8. A process according to claim 5 wherein saidrotating element is a solid having various cross-sectional areas in theplane transverse to gas flow.
 9. A process according to claim 5 whereinsaid rotating element is powered by power means driven by the energy ofthe gas stream flowing through said conduit.
 10. A process according toclaim 9 wherein said rotating element comprises a series of rotatablevanes whose axis of rotation is spaced a distance from the longitudinalcenter line of said conduit, and is substantially perpendicular to saidlongitudinal center line of said conduit.
 11. Apparatus for the heatingof surfaces by the combustion of fluids, said apparatus comprising thecombination: a. a surface to be heated, b. a combustion chambercommunicating with said surface, c. fuel inlet means communicating withsaid combustion chamber, d. oxygen-containing gas inlet meanscommunicating with said combustion chamber directed at an angle to saidfuel inlet means, e. conduit means communicating with at least one ofsaid fuel inlet means or oxygen-containing gas inlet means, f. pressurefluctuation means operably located in relation to said conduit so as tocause intermittent pressure variation in said conduit, whereby saidpressure variation causes a hot gas or flame stream produced by thecombustion of said fuel in contact with said oxygen-containing gases tomove across said surface to be heated.